In the field of lithographic printing, ink is continuously conveyed from an ink source through a series of rollers to a printing plate on a plate cylinder in a printing press. Image portions of the printing plate accept ink from one or more of the last of a series of inking rollers and transfer a portion of that ink to a blanket cylinder as a reverse image from which a portion of the ink is transferred to form a correct-reading image on paper or other materials. It is also important in conventional lithographic printing processes that a dampening solution containing water and proprietary additives be conveyed continuously to the printing plate whereby transferring in part to the non-image areas of the printing plate the water functions to keep those non-image areas free of ink. Finally, in conventional printing press systems, the ink is continuously made available in varying amounts determined by cross-press column input control adjustments to a plurality of ink metering devices, such as ink injectors. Open fountain inker systems may also be used as ink metering devices.
Lithographic printing plate surfaces in the absence of imaging materials have minute interstices and a hydrophilic or water-loving property to enhance retention of water, that is the dampening solution, rather than ink on the surface of the plate. Imaging the plate fills these interstices and creates oleophilic or ink-loving areas according to the image that is to be printed. Consequently, when both ink and dampening solution are presented to an imaged plate in appropriate amounts, only the ink tending to reside in non-image areas becomes disbonded from the plate. In general, this action accounts for the continuous ink and dampening solution differentiation on the printing plate surface, which is integral to the lithographic printing process.
It is necessary to control the correct amount of ink supplied from each of the ink injectors during lithographic printing. U.S. Pat. No. 5,027,706, the entire disclosure of which is hereby incorporated by reference, describes an inking system including controls for controlling supply of ink from an ink rail to a plurality of individual ink outlet orifices corresponding to ink columns or zones.
U.S. Pat. No. 5,179,978, the entire disclosure of which is hereby incorporated by reference, describes a rotary ink valve assembly for controlling ink or printing fluid input in a printing press.
U.S. 2006/0162597, the entire disclosure of which is hereby incorporated by reference, describes an integrated ink rail assembly which includes a plurality of page packs, each page pack including a corresponding ink outlet orifice corresponding to an ink column or zone.